Resin materials and films made therefrom

ABSTRACT

A resin material comprising a resin, which satisfies at least one relationship selected from the group consisting of the following relationships [I] and [II] is provided: 
     
       
         ln( OTR /22.5)+4.78 ln( Fy/Fy ′)&lt;−0.13, and  T   2   −T   1 ≦20  [I] 
       
     
     in which Fy′ is a yield strength of a standard saponified ethylene-vinyl acetate copolymer at 60° C.; Fy is a yield strength of the resin material at 60° C.; OTR is an oxygen gas permeability (cc/m 2 ·day·atm) of the resin material per a unit thickness of 1 μm at 23° C. and a relative humidity of 0%; T 1  is a haze (%) of a film of the resin material having a thickness of 30 μm after being maintained at 23° C. and a relative humidity of 48% for 48 hours; and T 2  is a haze (%) of a film of the resin material having a thickness of 30 μm after being maintained at 40° C. and a relative humidity of 90% for 24 hour, and 
     
       
         ln( OTR /22.5)+0.0698(T im −157)&lt;−0.06 [II] 
       
     
     in which OTR is an oxygen gas permeability (cc/m 2 ·day·atm) of the resin material per a unit thickness of 1 μmat 23° C. and a relative humidity of 0%; and T im  is a melting point of the resin material.

This application is the national phase of international applicationPCT/JP98/02018 filed May 7, 1998 which designated the U.S.

FIELD OF THE INVENTION

The present invention relates to a resin material having gas barrierproperties and a film comprising the same.

DESCRIPTION OF BACKGROUND ART

Shrink packaging using a stretched film (a heat-shrinkable film) iswidely used in industrial packaging such as packaging of foods,medicines, industrial parts, and the like. For example, a content ispackaged by inserting the content in the bag of a stretched film,optionally evacuating an air from the bag, sealing the opening of thebag, and then heating the bag to shrink the stretched film.

A film used in such shrink packaging is desired to shrink sufficientlyby heating. Furthermore, it is desired to lower a temperature at which afilm can be thermally shrunk from the viewpoint of the reduction ofpackaging process cycles.

A stretched film should be heated to a temperature higher than astretching temperature encountered in the production of the stretchedfilm to thermally shrink the stretched films. Thus, it is assumed thatthe thermally shrinking temperature of the stretched film may depend ona stretching temperature encountered in the production of the stretchedfilm.

Saponified ethylene-vinyl ester copolymers have better transparency andgas barrier properties, in particular, against oxygen gas, than otherresins. Therefore, the films of such saponified copolymers are widelyused in industrial packaging.

However, the saponified ethylene-vinyl ester copolymers, in particular,saponified ethylene-vinyl acetate copolymers, have high stiffness andthus less stretchability, in particular, at a low temperature, theyshould be stretched at a relatively high temperature. If they arestretched at a low temperature, they are split, unevenly stretched orwhitened, and thus stretched films having insufficient properties areobtained. Accordingly, it is desired to improve the stretchability ofsaponified ethylene-vinyl ester copolymers.

For example, JP-A-53-88067 and JP-A-59-20345 describe the improvement ofthe stretchability of saponified ethylene-vinyl ester copolymers by theaddition of various plasticizers. However, the improvement of thestretchability of saponified ethylene-vinyl ester copolymers by suchconventional methods are still unsatisfactory.

Hitherto, Nylon, polyvinylidene chloride, polyvinyl alcohol, liquidcrystal polymers and the like are used as gas barrier materials.However, it is known that Nylon and polyvinyl chloride have inferior gasbarrier properties to saponified ethylene-vinyl ester copolymers, whilepolyvinyl alcohol and liquid crystal polymers have inferiorstretchability to saponified ethylene-vinyl ester copolymers. Thus,those polymers having gas barrier properties do not have good balance ofgas barrier properties and stretchability.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a material having gasbarrier properties which are comparable with those of saponifiedethylene-vinyl ester copolymers, and better stretchability thansaponified ethylene-vinyl ester copolymers.

According to one aspect of the present invention, there is provided aresin material comprising a resin, which satisfies at least onerelationship selected from the group consisting of the followingrelationships [I] and [II]:

ln(OTR/22.5)+4.78 ln(Fy/Fy′)<−0.13, and T ₂ −T ₁<20  [I]

in which

Fy′ is a yield strength of a standard saponified ethylene-vinyl acetatecopolymer at 60° C.;

Fy is a yield strength of said resin material at 60° C.; OTR is anoxygen gas permeability (cc/m²·day·atm) of said resin material per aunit thickness of 1 μm at 23° C. and a relative humidity of 0%;

T ₁ is a haze (%) of a film of said resin material having a thickness of30 μm after being maintained at 23° C. and a relative humidity of 48%for 48 hours; and

T ₂ is a haze (%) of a film of said resin material having a thickness of30 μm after being maintained at 40° C. and a relative humidity of 90%for 24 hour, and

ln(OTR/22.5)+0.0698(T _(im)−157)<−0.06  [II]

in which

OTR is an oxygen gas permeability (cc/m²·day·atm) of said resin materialper a unit thickness of 1 μm at 23° C. and a relative humidity of 0%;and

T _(im) is a melting point of said resin material.

This and other embodiments of the present invention will be explained indetail.

PREFERABLE EMBODIMENTS OF THE INVENTION

One embodiment of the resin material according to the present inventioncomprises a resin as a main component, and satisfies the followinginequalities (1) and (2):

ln(OTR/22.5)+4.78 ln(Fy/Fy′)<−0.13  (1)

and

T ₂ −T ₁≦20  (2)

In the inequality (1), ln(OTR/22.5) is the natural logarithm of(OTR/22.5), and ln(Fy/Fy′) is the natural logarithm of (Fy/Fy′).

OTR is an oxygen gas permeability (cc/m²·day·atm) of the resin materialof the present invention per a unit thickness of 1 μm at 23° C. and arelative humidity of 0%. OTR is preferably less than 22.5, morepreferably 18 or less, in particular 11 or less.

Fy is a yield strength of the resin material of the present invention at60° C., and expressed by the yield strength of a test specimen (No. 1dumbbell defined by JIS K 6301) at 60° C., which is cut out from apressed sheet having a thickness of 300 μm obtained by heat pressing theresin material of the present invention at 200° C. for 3 minutes andcold pressing it at 30° C. for 5 minutes. A yield strength is read froma tensile stress-strain curve (namely S—S curve), which is drawn basedon the results of a tensile test carried out using a tensile tester inwhich the temperature of a test specimen can be controlled (for example,AGS 500D manufactured by Shimadzu Corporation) at a specimen temperatureof 60° C. at a pulling rate of 1,000 mm/min.

Fy′ is a yield strength of a standard saponified ethylene-vinyl acetatecopolymer at 60° C., and can be obtained in the same way as Fy exceptthat the standard saponified ethylene-vinyl acetate copolymer is used inplace of the resin material of the present invention.

When the inequality (1) is not satisfied, the oxygen gas permeability ofthe resin material is too high, that is, the gas barrier properties areinsufficient, the stretchability of the resin material at a lowtemperature is low, and thus, a high stretching temperature is requiredto sufficiently stretch the resin material. When the inequality (1) issatisfied, but the inequality (2) is not satisfied, the stretchabilityand/or gas barrier properties of the resin material are notsatisfactory. To achieve both good gas barrier properties andstretchability, ln(OTR/22.5)+4.78ln(Fy/Fy′) is preferably less than−0.4, more preferably less than −0.7.

Herein, a “standard saponified ethylene-vinyl acetate copolymer” means asaponified ethylene-vinyl acetate copolymer having an ethylene unitcontent of 44%, a saponification value of at least 98%, a melt index(MI) of 5.5 g/10 min., which is measured at 190° C. under a load of 2.16kg after preheating a sample at 190° C. for 6 minutes, an oxygen gaspermeability of 22.5 cc/m²·day·atm per a unit thickness of 1 μm at 23°C. and a relative humidity of 0%, and a melting point of 157° C.

An ethylene unit content is a ratio of the number of ethylene units tothe number of whole polymerized monomer units of a saponifiedethylene-vinyl acetate copolymer. The content of ethylene units and thesaponification value can be measured by an infrared absorption method.

A standard saponified ethylene-vinyl acetate copolymer may be obtainedby copolymerizing ethylene and vinyl acetate and saponifying thecopolymer so that the copolymer satisfies the above ethylene unitcontent, saponification degree and MI. One example of a commerciallyavailable standard saponified ethylene-vinyl acetate copolymer isEP-E105B which is produced by KURARAY CO., LTD. Saponifiedethylene-vinyl acetate copolymers, which are substantially the same asEP-E105B may be used as standard saponified ethylene-vinyl acetatecopolymers.

In the above inequality (2), T ₁ is a haze of a film of the resinmaterial of the present invention having a thickness of 30 μm afterbeing maintained at 23° C. and a relative humidity of 48% for 48 hours,and T ₂ is a haze of a film of the resin material of the presentinvention having a thickness of 30 μm after being maintained at 40° C.and a relative humidity of 90% for 24 hour. A film used to measure ahaze is prepared by heat pressing a resin material at 200° C. for 3minutes and then cool pressing at 30° C. for 5 minutes.

A haze is defined by the formula:

(Transmittance of scattered light)/Total light transmittance) ×100 (%)

and measured according to JIS K 7105. A smaller haze means bettertransparency of a resin material. T ₁ is preferably 4.9% or less, morepreferably 4% or less, from the viewpoint of the transparency of a resinmaterial.

The composition of the resin material according to the present inventionis not limited insofar as it contains a resin as a main component, andsatisfies the above inequalities (1) and (2).

In one preferred embodiment, the resin material of the present inventionconsists essentially of a resin as a main component, and containssubstantially no component other than the resin. In this embodiment, aresin may be a single resin, or a mixture of two or more resins.

In another preferred embodiment, the resin material of the presentinvention is a composition comprising a resin as a main component and acomponent or components other than the resin. This composition will bereferred to as a composite embodiment. Also in this embodiment, a resinas a main component may be a single resin or a mixture of two or moreresins.

In the composite embodiment, a component other than the above resin,which is used so that the composition satisfies the above inequalities(1) and (2), is referred to as “third component”. The compositeembodiment is preferred from the viewpoint of the easy control ofproperties such as gas barrier properties and stretchability of theresin material.

The resin material of the present invention may contain additives whichare conventionally compounded in resins, such as fillers, antistaticagents, stabilizers, nucleating agents, colorants, lubricants, rubbers,etc.

A resin used as the main component of the resin material of the presentinvention is not limited. Examples of resins include saponifiedpolyvinyl esters (e.g. polyvinyl alcohol, etc.), saponifiedethylene-vinyl ester copolymers (e.g. ethylene-vinyl alcohol, etc.),polyolefin resins (e.g. low density or high density polyethylene,ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexenecopolymer, ethylene-octene copolymer, polypropylene, etc.),ethylene-vinyl ester copolymers (e.g. ethylene-vinyl acetate copolymers,etc.), ethylene-(meth)acrylate copolymers (e.g. ethylene-methylmethacrylate copolymer, ethylene-methyl acrylate copolymer, etc.),ionomer resins, polyester resins (e.g. polyethylene terephthalate,polybutylene terephthalate, polyethylene naphthalate, polyhydroxybenzoicacid, etc.), polyamide resins (e.g. Nylon-6, Nylon-6,6,metaxylenediamine-adipic acid condensation polymer and its salts, etc.),aramid resins, acrylic resins (e.g. polymethyl methacrylate, polyacrylicacid, polysodium acrylate, poly-2-hydroxyethyl acrylate,poly-2-hydroxyethyl methacrylate, polyacrylamide, ethylene-acrylic acidcopolymer and its salts, etc.), styrene or acrylonitrile resins (e.g.polystyrene, styrene-acrylonitrile copolymer,styrene-acrylonitrile-butadiene copolymer, polyacrylonitrile, etc.),halogen-containing resins (e.g. polyvinyl chloride, polyvinylidenechloride, polyvinylidene fluoride, polytetrafluoroethylene, etc.),engineering plastics (e.g. polycarbonate resin, polysulfone resin,polyethersulfone resin, polyetheretherketone resin, polyphenylene oxideresin, polymethylene oxide, etc.), and the like. Furthermore, modifiedresins may be used, which are prepared by graft-modifying orcrosslinking the above resins, or by modifying the molecular chain endsof the above resins.

Preferred examples of the resin material of the present invention are aresin material consisting of a modified saponified ethylene-vinyl estercopolymer which is obtained by graft-modifying, crosslinking orchain-end-modifying a saponified ethylene-vinyl ester copolymer, and acomposition comprising a saponified ethylene-vinyl ester copolymer andthe third component. The latter composition is particularly preferred.The vinyl ester units of the saponified ethylene-vinyl ester copolymerare preferably vinyl acetate units.

The content of ethylene units in a saponified ethylene-vinyl estercopolymer which is preferably used in the present invention ispreferably from about 20% to about 60%, more preferably from about 20%to about 45%, in particular from about 25% to about 40%, based on thetotal number of polymerized monomer units, from the viewpoint of themoisture resistance of the resin material.

The saponification value of the vinyl ester components is usually atleast about 90%, preferably at least about 95%, more preferably at leastabout 98%.

When the resin material of the present invention is a compositioncomprising a saponified ethylene-vinyl ester copolymer and the thirdcomponent, the content of the saponified ethylene-vinyl ester copolymeris preferably from 99 to 50 wt. % of the whole composition from theviewpoint of the gas barrier properties, processability andstretchability of the resin material.

One preferred example of the third component, which is used incombination with a saponified ethylene-vinyl ester copolymer, is analcohol having a 1,3-diol structure of the following formula (3) havinga solubility parameter (SP) and a molecular weight (MW) which satisfythe following inequalities (4) and (5), from the viewpoint of acompatibility with the saponified ethylene-vinyl ester copolymer:

 SP≧12  (4)

SP×MW ^(1/2) ≧225  (5)

In the formula (3), R₁ to R₆ are the same or different and represent ahydrogen atom, or an atomic group composed of at least two atomsselected from the group consisting of hydrogen, carbon, nitrogen,oxygen, phosphorus and sulfur atoms, provided that the total atomicweight of atoms constituting R₂ is more than that of atoms constitutingR₁.

A solubility parameter (SP) is described in POLYMER ENGINEERING ANDSCIENCE, Vol. 14, No. 2 (1974) 147-154, the disclosure of which ishereby incorporated by reference, and defined by the following equation(6):

SP=(ΔEv/V)^(1/2)  (6)

wherein ΔEv is a molar cohesive energy (cal/mol), which is defined bythe equation (7):

ΔEv=Σe _(i)  (7)

and V is a molar volume defined by the equation (8):

 V=ΣΔv _(i)  (8)

wherein e_(i) and v_(i) are the values listed in Table 5 of theabove-described literature.

One preferable resin material of the present invention can contain atleast one of the above-defined alcohols. When a resin material containstwo or more alcohols, SP is an averaged solubility parameter defined bythe following equation (9), and MW is a weight average molecular weightdefined by the following equation (10):

SP=(Σα_(i) ΔEv _(i)/Σα_(i) V _(i))^(1/2)  (9)

wherein ΔEv_(i) and Vi are a molar cohesive energy (cal/mol) and a molarvolume (cm³/mol) of each alcohol, respectively, and α_(i) is a molarfraction of each alcohol in the whole alcohols,

MW=Σφ _(i) mw _(i)  (10)

wherein φ_(i) and mw_(i) are a weight fraction of each alcohol in thewhole alcohols, and a molecular weight of each alcohol, respectively.

When the resin material of the present invention contains the abovealcohol(s), SP of the alcohol(s) is preferably at least about 13 fromthe viewpoint of the compatibility of the alcohol(s) with the resin. Theupper limit of SP is about 20. SP×MW^(1/2) is preferably at least about235, from the viewpoint of the suppression of bleeding of the alcohol(s). The upper limit of SP×MW^(1/2) is about 20,000.

In the formula (3), R₁ to R₆ represent a hydrogen atom, or an atomicgroup composed of at least two atoms selected from the group consistingof hydrogen, carbon, nitrogen, oxygen, phosphorus and sulfur atoms. Thetotal atomic weight of atoms constituting R₂ is more than that of atomsconstituting R₁, R₁ to R₆ may the same or different. R₁ to R₆ areselected so that SP and MW satisfy tie above equations (4) and (5).Typical examples of the atomic groups include atomic groups such asalkyl groups, cycloalkyl groups, atomatic hydrocarbons, heterocyclicgroups, etc.; functional groups such as a hydroxyl group, a nitrosogroup, a sulfinyl group, a sulfonyl group, a phosphino group, aphosphonyl group, etc.; and atomic groups having at least one functionalgroup.

Preferably, R₁ is a hydrogen atom, or a hydroxyalkyl group, an alkylgroups, an amino group or an atomic group having an amino group. Inparticular, R₁ is a methylol group; a methyl group, an ethyl group or anamino group.

Preferably, R₂ is an atomic group having a hydroxyl group and a totalatomic weight of the constituting atoms of at least 31.

Preferably, R₃ to R₆ are each a hydrogen atom or a low alkyl group. Apreferred lower alkyl group is an alkyl group having 1 to 6 carbonatoms, in particular, a methyl group or an ethyl group.

Examples of the alcohol used in the present invention includepolypentaerithritols (e.g. dipentaerithritol, tripentaerithritol, etc.),polytrimethylolmethanes (e.g. ditrimethylolmethane,tritrimethylolmethane, etc.), polytrimethylolethanes (e.g.ditrimethylolethane, tritrimethylolethane, etc.),polytrimethylolpropanes (e.g. ditrimethylolpropane,tritrimethylolpropane, tetratrimethylolpropane, pentatrimethylolpropane,etc.), poly-2-amino-2-hydroxymethyl-1,3-propanediols (e.g.di-2-amino-2-hydroxymethyl-1,3-propanediol,tri-2-amino-2-hydroxymethyl-1,3-propanediol, etc.), and the like.

The third component may be an ester of an alcohol and a carboxylic acid(e.g. a monocarboxylic acid, a dicarboxylic acid or a tricarboxylicacid) having a 1,3-diol structure.

Examples of monocarboxylic acids include aliphatic monocarboxylic acids(e.g. acetic acid, propionic acid, butyric acid, valeric acid, caproicacid, enanthic acid, caprylic acid, capric acid, pelargonic acid,undecanoic acid, lauric acid, tridecanoic acid, myristic acid,myristoleic acid, palmitic acid, stearic acid, oleic acid, linoleicacid, arachidic acid, behenic acid, etc.), alicyclic monocarboxylicacids (e.g. cyclohexanecarboxylic acid, methylcyclohexnanecarboxylicacid, etc.), aromatic monocarboxylic acids (e.g. benzoic acid, toluicacid, ethylbenzoic acid, phenylacetic acid, etc.).

Examples of dicarboxylic acids include aliphatic dicarboxylic acids(e.g. malonic acid, succinic acid, glutaric acid, adipic acid, pimelicacid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid,tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid,octadecenedioic acid, eicosanedioic acid, eicosenedioic acid,docosanedioic acid, 2,2,4-trimethyladipicacid, etc.),alicyclicdicarboxylic acids (e.g. 1,4-cyclohexanedicarboxylic acid,etc.), aromatic dicarboxylic acids (e.g. terephthalic acid, isophthalicacid, phthalic acid, xylynedicarboxylic acid, etc.), and the like.

Examples of tricarboxylic acids include 1,2,3-propanetricarboxylic acid,aconitic acid, and the like.

Preferred examples of alchols include polytrimethylol-propaneanddipentaerithritol. In particular, a dimer, a trimer, a tetramer or apentamer of trimethylolpropane are preferred.

When the resin material of the present invention is a compositioncomprising a saponified ethylene-vinyl ester copolymer and two or morealcohols, the composition preferably contains at least one alcoholhaving a solubility parameter sp, and a molecular weight mw_(i), whichsatisfy the following inequalities:

sp _(i)≧16, and sp _(i) ×mw _(i) ^(1/2)≧280

Such an alcohol will be referred to as “specific alcohol”. Thecomposition preferably contains at least 20 wt. % of a specific alcoholbased on the whole alcohols. Preferably, the amount of the specificalcohol does not exceed 70 wt. % of the whole alcohols to avoid thebleeding of the alcohol (s) from the surface of the composition. Thespecific alcohol is preferably polypentaerithritol, in particular,dipentaerithritol.

The resin material of the present invention may contain, as a maincomponent, a modified resin prepared by the reaction of a resin and thethird component (for example, a modified product of a saponifiedethylene-vinyl ester copolymer, which is obtained by the reaction of thesaponified ethylene-vinyl ester copolymer and an alcohol), or acopolymer obtained by the copolymerization of a copolymerizable thirdcomponent and a copolymerizable monomer.

A modified resin can be prepared by a conventional graft-modificationmethod, for example, a method comprising forming apolymerization-initiating site on a backbone polymer and polymerizingthe third component monomer, or the reaction of a resin and thepolymerizable third component. The graft reaction maybe carried out in ahomogeneous system (for example, a reaction in a solution), or aheterogeneous system (for example, a solid-liquid reaction). A modifiedresin may be prepared by the conventional crosslinking of a backbonepolymer using a crosslinking agent or heat. Furthermore, a modifiedresin may be prepared by the conventional modification of chain ends ofa backbone polymer by introducing a functional atomic group into thebackbone polymer when the polymerization reaction of the backbonepolymer is terminated. The preparation of such a modified resin may becarried out with an extruder.

When the resin material of the present invention is a compositioncomprising at least one resin, it may be prepared by a melt-kneadingextrusion method using a conventional single- or twin-screw extruderwhich is commonly used to knead resins. When a viscous fluid thirdcomponent is used in the course of the preparation of the resinmaterial, the third component is dissolved in a solvent (e.g. water ororganic solvents) and then supplied to the kneading step. In this case,the resin material of the present invention may be prepared by a methodcomprising the steps of pouring the solution of the third component intothe midsection of the cylinder of an extruder while kneading a resin inthe cylinder, and then further kneading the resin and the thirdcomponent in the downstream zone of the cylinder, or a method comprisingthe steps of blending resin pellets and the solution of the thirdcomponent with a mixer such as a Henschel mixer, and then supplying themixture in an extruder to knead the mixture. Alternatively, the resinmaterial of the present invention may be prepared by blending thepellets of a master batch containing the third component in a highconcentration with resin pellets, and then melting and kneading themixture with an extruder.

When the third component is a powder, the resin material of the presentinvention can be prepared by a method comprising the steps of dryblending resin pellets and the third component and supplying the mixturein an extruder to melt and knead the mixture, or a method comprisingsupplying the third component powder and resin pellets directly in anextruder to melt and knead them.

Apart from a resin material which satisfies the above inequalities (1)and (2), a resin material, which satisfies the following inequality(11), has good gas barrier properties and stretchability at a lowtemperature:

ln(OTR/22.5)+0.0698(T _(im)−157)<−0.06  (11)

wherein OTR is an oxygen gas permeability (cc/m²·day·atm) of the resinmaterial per a unit thickness of 1 μm at 23° C. and a relative humidityof 0%, and T _(im) is a melting point of the resin material.

Amelting point T _(im) is measured with a differential scanningcalorimeter according to JIS K 7121. Prior to the measurement of amelting point, a sample is maintained in the calorimeter at atemperature of 23° C. and a relative humidity of 50% for 24 hours ormore, and then subjected to a pretreatment. In the pretreatment, thesample is heated in the calorimeter to a temperature 30° C. higher thana temperature at which the sample shows a melting peak (hereinafterreferred to as “maximum temperature”), maintained at the maximumtemperature for 10 minutes, and cooled to a temperature 50° C. lowerthan a temperature at which the sample shows a transition peak at acooling rate of 10°/min. After this pretreatment, a melting point ismeasured. In the measurement of a melting point, the pretreated sampleis heated at a heating rate of 10° C./min. until at least one meltingpeak is observed. A melting point (T _(im)) is defined as a temperaturecorresponding to a point of intersection between a line which isextended in the direction on the higher temperature side from a baseline on the lower temperature side of the melting peak, and a tangentline having the steepest slope on the curve of the melting peak on thelower temperature side.

The value of ln(OTR/22.5)+0.0698 (T _(im)−157) is preferably less than−0.1, in particular, less than −0.4, to achieve both good gas barrierproperties and stretchability.

The resin material of the present invention can be processed to producevarious products. In particular, the resin material can be used as amaterial of a gas barrier film because of good gas barrier propertiesand stretchability.

In one embodiment of a gas barrier film, the film is a single layer filmof the resin material of the present invention. In a further embodimentof a gas barrier film, the film is a multi-layer film comprising atleast one layer of the resin material of the present invention, and atleast one layer of other material than the resin material of the presentinvention. The layer of the other material may be made of resins,metals, paper, fabrics, etc. The layer structure of the multi-layer filmis not limited. One typical example of the multi-layer film is a filmcomprising a layer of a substrate resin, a layer of a thermal bondingresin, and a layer of the resin material of the present inventioninterposed between them. Such a multi-layer film may have one or moreadditional layers depending on desired film properties.

The thickness of a film is usually from about 10 μm to about 500 μm. Thethickness of a film suitable for packaging is usually from about 15 μmto about 100 μm. In the case of a multi-layer film, the thickness of thelayer of the resin material according to the present invention ispreferably from about 5% to about 30% of the total thickness of themulti-layer film, from the viewpoint of a balance between effects andcosts.

When a multi-layer film has a substrate resin layer formed from amaterial other than the resin material of the present invention, thesubstrate resin layer may be formed from a polyolefin resin (e.g. lowdensity polyethylene, high density polyethylene, ethylene-propylenecopolymer, ethylene-butene copolymer, ethylene-hexene copolymer,etylene-octene copolymer, polypropyrene, etc.), an ethylene-vinyl estercopolymer (e.g. ethylene vinyl acetate, etc.), anethylene-(meth)acrylate copolymer (e.g. ethylene-methyl methacrylatecopolymer, etc.) an ionomer resin, a polyester resin (e.g. polyethyleneterephthalate, polybutyrene terephthalate, polyethylene naphthalate,etc.), a polyamide resin (e.g. Nylon-6, Nylon-6,6,metaxylenediamine-adipic acid condensation polymer,polymethylmetacrylimide, etc.), an acrylic resin (e.g. polymethylmethacrylate, etc.), a styrene or acrylonitrile resin (e.g. polystyrene,styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadienecopolymer, polyacrylonitrile, etc.), a hydrophobic cellulose resin (e.g.cellulose triacetate, cellulose diacetate, etc.), a halogen-containingresin (e.g. polyvinyl chloride, polyvinylidene chloride, polyvinylidenefluoride, polytetrafluoroethylene, etc.), a hydrogen-bonding resin (e.g.polyvinyl alcohol, ethylene-vinyl alcohol copolymer, cellulosederivative, etc.), an engineering plastic (e.g. polycarbonate resin,polysulfone resin, polyethersulfone resin, polyetheretherketone resin,polyphenylene oxide resin, polymethylene oxide, liquid crystal polyesterresin, etc.), and the like. Among them, polyolefin resins, inparticular, polyethylene and polypropylene are preferable from theviewpoint of strength.

Examples of resins for a thermal bonding layer include polyolefin resins(e.g. low density polyethylene, high density polyethylene,ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexenecopolymer, ethylene-4-methyl-1-pentene copolymer, etylene-octenecopolymer, polypropyrene, etc.), ethylene-vinyl ester copolymers (e.g.ethylene vinyl acetate, etc.), ethylene-(meth)acrylate copolymers (e.g.ethylene-methyl methacrylate copolymer, ethylene-methyl acrylatecopolymer, etc.), ethylene-vinylcarboxylic acid copolymers (e.g.ethylene-acrylic acid copolymer, etc.), ionomer resins, saponifiedethylene-vinyl ester copolymers (e.g. ethylene-vinyl alcohol copolymer,etc.), polyamide resins (e.g. Nylon-6, Nylon-6, 6, etc.), styreneoracrylonitrile resins (e.g. polystyrene, styrene-acrylonitrile copolymer,styrene-acrylonitrile-butadiene copolymer, polyacrylonitrile, etc.),polyacrylates (e.g. polymethyl methacrylate, etc.), and the like.

The layer of an adhesive resin may preferably be formed to produce amulti-layer film having a good interlaminar bond strength. An adhesiveresin is not limited, and may be a modified polyolefin polymer having acarboxyl group, which is prepared by chemically bonding an unsaturatedcarboxylic acid or its anhydride to an olefin polymer. Preferredexamples of such a modified olefin polymer include polyethylene graftmodified with maleic anhydride, polypropylene graft modified with maleicanhydride, ethylene-ethyl acrylate copolymer modified with maleicanhydride, ethylene-vinyl acetate modified with maleic anhydride,ethylene-acrylic acid copolymer modified with maleic anhydride, andionomer resin modified with maleic anhydride.

A single-layer film may be produced by any conventional molding methodsuch as extrusion. A multi-layer film may be produced by co-extrusion,melt coating, extrusion lamination, dry lamination, and the like.

A film may be an unstretched film or a stretched film, and either filmcan be used for packaging. In particular, a stretched film having heatshrinking properties is preferably used for shrink packaging.

As a method for the production of a stretched film, conventionalstretching methods such as uniaxial stretching, zone stretching, flatsequential stretching, simultaneous biaxial stretching, tubularstretching and the like are exemplified. Among them, tubular stretchingis preferably employed from the viewpoint of plant investment.

Besides films, the resin material of the present invention can be shapedin various products such as sheets, tubes, cups, bottles, etc. Toproduce such products, any conventional molding methods, for example,hot molding (e.g. vacuum molding, drawing, air-pressure forming, etc.),injection molding, blow molding, stretch-blow molding, and the like, maybe employed.

The produced molded articles are suitable as containers for packaginggeneral foodstuffs, retort foodstuffs, medicines, electronic parts,gasoline, etc. A multi-layer film comprising a layer of the resinmaterial of the present invention and a layer of a thermal bonding resinis particularlyuseful as a heat-shrinkable film.

The resin material of the present invention has gas barrier propertiescomparable to or better than those of conventional ethylene-vinyl estercopolymers, and better stretchability than that of the conventionalethylene-vinyl ester copolymers. Furthermore, the resin material of thepresent invention has good transparency, and suffers less deteriorationof transparency over time.

EXAMPLES

The present invention will be illustrated by the following examples,which do not limit the scope of the invention in any way.

Various properties are measured as follows:

[Oxygen Gas Permeability]

The oxygen gas permeability of a resin material was measured accordingto JIS K 7126.

A resin material was heat pressed at 200° C. for 3 minutes and then coldpressed at 30° C. for 5 minutes to prepare a test sheet. Then, theoxygen gas permeability of the test sheet was measured with anoxygen-permeability measuring instrument (OX-TRAN 10/50A manufactured byMOCON, USA).

The oxygen gas permeability of the test sheet was continuously measured,and the gas permeability value, which was obtained when the gaspermeability became substantially constant, was used as the oxygen gaspermeability of the test sheet.

In the above testing, it took several hours to about 3 days from thestart of the measurement to the substantial stabilization of the oxygengas permeability. The measurement was carried out at 23° C. and arelative humidity of 0%. Then, the oxygen gas permeability per a unitthickness of 1 μm was calculated from the measured oxygen permeabilityvalue, and used as “OTR”. The unit of OTR is “cc/m²·day·atm”.

[Yield Strength and Elongation at Break]

The yield strength of a resin material was measured at 60° C. by thefollowing method according to JIS K 7113

A resin material was heat pressed at 200° C. for 3 minutes and then coldpressed at 30° C. for 5 minutes to prepare a film having a thickness of300 μm. Then, a test specimen in the form of No. 1 dumbbell defined byJIS K 6301 was cut out from the film.

Using a tensile tester (AGS 500D manufactured by Shimadzu Corporation)in which the temperature of a test specimen can be controlled, the testspecimen was pulled at a specimen temperature of 60° C. at a pullingrate of 1,000 mm/min. until the specimen was broken. Then, a yieldstrength Fy (kg/cm²) at 60° C. was read from a tensile stress-straincurve (S—S curve)

In the above measurement of tensile strength, a distance between gagemarks marked on the test specimen was measured before and after themeasurement, and an elongation at break l (%) was calculated accordingto the following formula:

l=[(L−L ₀)/L₀]×100

wherein L₀ is a distance between gage marks on the specimen beforemeasurement, and L is a distance between gage marks at break.

The larger l (elongation at break) means a larger stretching ratio at60° C., and thus a resin material has better stretchability.

Separately, a yield strength was measured with a test specimen, whichhad been prepared by the same method as above from a standard saponifiedethylene-vinyl acetate copolymer having an ethylene unit content of 44%,a saponification value exceeding 98%, a melt index MI of 5.5 g/10 min.,an oxygen gas permeability of 22.5 cc/m²·day·atm per a thickness of 1 μmat 23° C. and a relative humidity of 0%, and a melting point of 157° C.(EP-E105B manufactured by KURARAY Co., Ltd., hereinafter referred to as“EVOH-E”). The yield strength Fy′ was 296 kg/cm².

[T ₁]

A resin material was heat pressed at 200° C. for 3 minutes and then coldpressed at 30° C. for 5 minutes to prepare a film having a thickness of30 μm. This film was maintained at 23° C. and a relative humidity of 48%for 48 hours, and then its haze T ₁ was measured according to JIS K7105. The measurement of a haze was carried out using a direct-readinghaze computer (HGM-DP manufactured by SUGA SHIKENKI KABUSHIKIKAISHA).

[T ₂]

A film having a thickness of 30 μm, which had been prepared in the samemanner as above, was maintained at 40° C. and a relative humidity of 90%for 24 hours, and then its haze T ₂ was measured.

[Evaluation of Stretchability]

A resin material having substantially the same (±2%) elongation at breakas that of the standard saponified ethylene-vinyl acetate copolymer wasranked “B”, one having larger elongation at break than the above wasranked “A”, and one having less elongation at break than the above wasranked “C”.

[Evaluation of Gas Barrier Properties]

A resin material having substantially the same (±10%) oxygen gaspermeability as that of the standard saponified ethylene-vinyl acetatecopolymer was ranked “B”, one having less oxygen gas permeability thanthe above was ranked “A”, and one having larger oxygen gas permeabilitythan the above was ranked “C”.

[Total Evaluation]

In relative comparisons, a resin material having an excellent balance ofthe evaluation of stretchability and the evaluation of gas barrierproperties was ranked “A”, one having a good balance was ranked “B”, andone having a low balance was ranked “C”.

Example 1

Dipentaerithritol (DIPENTALID manufactured by KOEI Chemical Co., Ltd.,hereinafter referred to as “DP”) and ditrimethyloipropane (manufacturedby KOEI Chemical Co., Ltd., hereinafter referred to as “DTMP”) weremixed in a weight ratio of 1:1. DP had sp_(i) of 18.7, mw_(i) of 272,and (sp_(i)×mw_(i) ^(1/2)) of 308, and DTMP had sp_(i) of 14.4, mw_(i)of 250, and (sp_(i)×mw_(i) ^(1/2)) of 228. Thus, the mixture had anaverage solubility parameter SP of 16.4, a weight average molecularweight MW of 261, and (Sp×MW^(1/2)) of 265.

The above mixture and the standard saponified ethylene-vinyl acetatecopolymer (EVOH-E) were dry blended in a weight ratio of 10:90, and theobtained mixture was melted and kneaded with a twin-screw extruder (40mmφ extruder BT-40-S2-60-L manufactured by KABUSHIKIKAISHA PLASTICKOGAKU KENKYUUSHO; L/D=60) to obtain the composition. The results of theevaluations of the composition are shown in Table 1.

Example 2

A composition was prepared in the same manner as in Example 1 exceptthat a saponified ethylene-vinyl acetate copolymer having an ethyleneunit content of 38% and a saponfication value exceeding 98% (ES-H101Bmanufactured by KURARAY CO., LTD., hereinafter referred to as “EVOH-H”)in place of EVOH-E. The results of the evaluations of the compositionare shown in Table 1.

Example 3

A composition was prepared in the same manner as in Example 1 exceptthat a saponified ethylene-vinyl acetate copolymer having an ethyleneunit content of 32% and a saponfication value exceeding 98% (EP-F101Amanufactured by KURARAY CO., LTD., hereinafter referred to as “EVOH-F”)in place of EVOH-E. The results of the evaluations of the compositionare shown in Table 1.

Example 4

A composition was prepared in the same manner as in Example 1 exceptthat DTMP and EVOH-E were dry blended in a weight ratio of 10:90. Theresults of the evaluations of the composition are shown in Table 1.

Example 5

A composition was prepared in the same manner as in Example 2 exceptthat DTMP and EVOH-H were dry blended in a weight ratio of 10:90. Theresults of the evaluations of the composition are shown in Table 1.

Example 6

A composition was prepared in the same manner as in Example 3 exceptthat DTMP and EVOH-F were dry blended in a weight ratio of 10:90. Theresults of the evaluations of the composition are shown in Table 1.

Comparative Example 1

The results of the evaluations of the standard saponified ethylene-vinylacetate copolymer (EVOH-E) are shown in Table 1.

Comparative Example 2

The results of the evaluations of EVOH-H are shown in Table 1.

Comparative Example 3

The results of the evaluations of EVOH-F are shown in Table 1.

Comparative Example 4

A composition was prepared in the same manner as in Example 3 exceptthat diglycerin and EVOH-E were dry blended in a weight ratio of 10:90.The results of the evaluations of the composition are shown in Table 1.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 C.E. 1 C.E. 2 C.E. 3 C.E. 4Gas barrier material Resin EVOH-E EVOH-H EVOH-F EVOH-E EVOH-H EVOH-FEVOH-E EVOH-H EVOH-F EVOH-E Ethylene content (mol %) 44 38 32 44 38 3244 38 32 44 Amount (wt. %) 90 90 90 90 90 90 100 100 100 90 CompoundDTMP DTMP DTMP DTMP DTMP DTMP — — — Diglycerin Amount (wt. %) 5 5 5 1010 10 — — — 10 Compound DP DP DP DP DP DP — — — — Amount (wt. %) 5 5 5 00 0 0 0 0 0 SP 16.4 16.4 16.4 14.4 14.4 14.4 — — — 18.3 MW 261 261 261250 250 250 — — — 166 SP × MW^(1/2) 265 265 265 228 228 228 — — — 236Physical Properties Fy (yield strength) 269 291 277 216 228 290 296 336388 170 (kg/cm²) OTR 16.5 7.9 4.3 17.1 7.2 7.2 22.4 10.8 5.9 124.5 C¹⁾−0.77 −1.13 −1.97 −1.78 −2.39 −1.24 0.00 −0.13 −0.05 −0.94 T₁ 2.6 3.74.0 4.0 4.0 4.2 5.0 5.7 6.1 11.3 T₂ 0 0 0 20 19 16 0 0 0 75 T₂-T₁ −2.6−3.7 −4 16 15 12 −5 −5.7 −6.1 63.7 Transparency A A A A A A B B B CElongation at break (%) 665 623 638 685 714 601 605 476 433 600Stretchability A A A A A B B C C B Stretchability/ A/A A/A A/A A/A A/AB/A B/B C/A C/A B/C gas barrier property Total evaluation A A A A A A-BB B-C B-C C Note: ¹⁾C = ln(OTR/22.5) + 4.78ln(Fy/Fy′).

What is claimed is:
 1. A resin material comprising (a) a resin comprisedof a saponified ethylene-vinyl ester copolymer and (b) at least onealcohol having a 1,3-diol backbone represented by the formula:

wherein R₁ represents a group selected from the group consisting of ahydrogen atom, a hydroxyalkyl group, an alkyl group, an amino group andan atomic group having an amino group; R₂ represents an atomic grouphaving both a hydroxyl group and a total atomic weight of itsconstituent atoms of at least 31; R₃ to R₆ represent a hydrogen atom ora lower alkyl group, said atomic groups being composed of at least twoatoms selected from the group consisting of hydrogen, carbon, nitrogen,oxygen, phosphorus and sulfur atoms, and said alcohol having asolubility parameter (SP) in (cal/cm³)^(1/2) and a molecular weight (MW)which satisfy the following inequalities: SP≧12 SP×MW≧235, with theproviso that when there are at least two alcohols, SP and MW are anaveraged solubility parameter and a weight average molecular weightrespectively, and wherein said mater satisfies at least one relationshipselected from the group consisting of the following relationships (I)and (II) ln(OTR22.5)+4.78 ln(Fy/Fy′)<−0.13, and T ₂ −T ₁≦20  (I) inwhich Fy′ is a yield strength of a standard saponified ethylene-vinylacetate copolymer at 60° C.; Fy is a yield strength of said resinmaterial at 60-C; OTR is an oxygen gas permeability (cc/m²·day·atm) ofsaid resin material per a unit thickness of 1 μm at 23° C. and arelative humidity of 0%; T ₁ is a haze (%) of a film of said resinmaterial having a thickness of 30 μm after being maintained at 23° C.and a relative humidity of 48% for 48 hours; and T ₂ is a haze (%) of afilm of said resin material having a thickness of 30 μm after beingmaintained at 40° C. and a relative humidity of 90% for 24 hour; andln(OTR/22.5)+0.0698(T _(im)−157)<−0.06  (II)  in which OTR is an oxygengas permeability (cc/m²·day·atm) of said resin material per a unitthickness of 1 μm at 23° C. and a relative humidity of 0%; and T _(im)is a melting point of said resin material.
 2. The resin materialaccording to claim 1, which satisfies the following inequality: ln(OTR/22.5)+4.78 ln(Fy/Fy′)<−0.4.
 3. The resin material according toclaim 1, which satisfies the following inequality: ln(OTR/22.5)+4.78ln(Fy/Fy′)<−0.7.
 4. The resin material according to claim 1, wherein T ₁is 4.9% or less.
 5. The resin material according to claim 1, whereinsaid saponified ethylene-vinyl ester copolymer comprises about 99% toabout 50% of the whole resin material.
 6. The resin material accordingto claim 1, wherein the SP is at least
 13. 7. The resin materialaccording to claim 1, wherein said alcohol satisfies the followinginequality: 235<SP×MW ^(1/2)≦20,000.
 8. The resin material according toclaim 1, wherein R₁ is a hydroxymethyl group.
 9. The resin materialaccording to claim 1, wherein R₁ is a methyl group or an ethyl group.10. The resin material according to claim 1, wherein said atomic grouphaving a hydroxyl group has an ether bond in the atomic group.
 11. Theresin material according to claim 1, wherein R₃ to R₆ are each ahydrogen atom or a lower alkyl group.
 12. The resin material accordingto claim 1, wherein R₃ to R₆ are each a methyl or an ethyl group. 13.The resin material according to claim 1, wherein said compositioncontains at least two alcohols, and at least one of the alcoholssatisfies the following inequalities: sp _(i)≧16, and sp _(i) ×MW_(i)≧280 wherein sp_(i) is a solubility parameter of an alcohol, andmw_(i) is a molecular weight of an alcohol.
 14. The resin materialaccording to claim 13, wherein at least one of the alcohols is a dimer,a trimer, a tetramer or a pentamer of trimethylolpropane.
 15. The resinmaterial according to claim 13, wherein at least one alcohol isdipentaerithritol.
 16. A resin material according to claim 1, whereinsaid atomic group is selected from the group consisting of a hydoxylgroup, a carbonyl group, a carboxyl group, an amino group, a nitrogroup, a nitroso group, a sulfinyl group, a sulfonyl group, a phosphinogroup, and a phosphonyl group.
 17. A resin material comprising (a) aresin comprised of a saponified ethylene-vinyl ester copolymer and (b)at least one alcohol having a 1,3-diol structure, said alcoholcomprising polytrimethylolpropane, wherein said material satisfies atleast one relationship selected from the group consisting of thefollowing relationships (I) and (II) ln(OTR/22.5)+4.78 ln(Fy/Fy′)<−0.13,and T ₂ −T ₁≦20  (I) in which Fy′ is a yield strength of a standardsaponified ethylene-vinyl acetate copolymer at 60° C.; Fy is a yieldstrength of said resin material at 60° C.; OTR is an oxygen gaspermeability (cc/m²·day·atm) of said resin material per a unit thicknessof 1 μm at 23° C. and a relative humidity of 0%; T ₁ is a haze (%) of afilm of said resin material having a thickness of 30 μm after beingmaintained at 23° C. and a relative humidity of 48% for 48 hours; and T₂ is a haze (%) of a film of said resin material having a thickness of30 μm after being maintained at 40° C. and a relative humidity of 90%for 24 hours; and ln(OTR/22.5)+0.0698(T _(im)−157)<−0.06  (II)  in whichOTR is an oxygen gas permeability (cc/m^(2·)day·atm) of said resinmaterial per a unit thickness of 1 μm at 23° C. and a relative humidityof 0%, and T _(im) is a melting point of said resin material.
 18. A filmconsisting of a resin material of any one of claims 1 to 4, 5, 6-7, 8-9,10-13 and 14-15.
 19. A multi-layer film comprising at least one layer ofa resin material of any one of claims 1 to 4, 5, 6-7, 8-9, 10-13 and14-15.
 20. A film comprising a layer of a resin material of any one ofclaims 1 to 4, 5, 6-7, 8-9, 10-13 and 14-15, and a thermal bondinglayer.
 21. The multi-layer film according claim 19 having heat shrinkingproperties.
 22. The resin material according to claim 1, wherein thecomposition consists essentially of a saponified ethylene-vinyl estercopolymer and at least one 1,3-diol compound represented by the formula:

wherein R₁ to R₆ are the same or different and represent hydrogen atomor an alkyl group provided that the total atomic weight of atomsconstituting R₂ is more than that of atoms constituting R₁.
 23. A filmconsisting of a resin material of claim
 17. 24. A multi-layer filmcomprising at least one layer of a resin material according to claim 17.25. A film comprising a layer of a resin material according to claim 17,and a thermal bonding layer.